The present invention relates to a storage system and a remote copy control method, and, for instance, can be suitably applied to a storage system that performs remote copy of data between a storage apparatus installed at an operation base and a storage apparatus installed at a remote base.
Today, remote copy technology is widely used particularly in systems of major corporations and government agencies in order to protect data from major natural disasters such as earthquakes or hurricanes, disasters resulting from acts of human beings such as erroneous operation by the system operator or terrorist attacks, and malfunctions of machinery and programs.
In addition, the data volume handled by businesses in recent years is of an increasing trend, and the number of storage apparatuses subject to remote copy is consequently increasing. Thus, needs for remote copy technology capable of replicating data at a remote base while maintaining the sequencing and consistency of the input and output data in large-scale storage systems are on the rise.
In view of such needs, for example, Japanese Patent Laid-Open Publication No. 2005-267216 (Patent Document 1) and Japanese Patent Laid-Open Publication No. 2006-318491 (Patent Document 2) describe remote copy technology of dividing a plurality of data volumes respectively provided by a plurality of storage apparatuses (hereinafter referred to as the “primary storage apparatus(es)”) installed at an operation base into a plurality of groups (hereinafter referred to as the “primary journal group(s)”), dividing a plurality of data volumes respectively provided by a plurality of storage apparatuses (hereinafter referred to as the “secondary storage apparatus(es)”) installed at a remote base into a plurality of groups (hereinafter referred to as the “secondary journal group(s)”) in correspondence with the foregoing primary journal groups, and performing asynchronous remote copy between the corresponding primary journal group and the secondary journal group.
With the foregoing remote copy technology, when data is written into the data volume of the primary storage apparatus, update history information of the data volume referred to as a journal containing the written data as well as the position and time (time stamp) of the written data is created in the primary storage apparatus.
Meanwhile, the secondary storage apparatus periodically sends a transfer request of the journal (hereinafter referred to as the “journal transfer request”) to the corresponding primary storage apparatus. The secondary storage apparatus additionally writes the data contained in the journal transferred from the primary storage apparatus according to the journal transfer request to the corresponding position of the corresponding data volume in the self storage apparatus (this process is hereinafter referred to as “reflecting the journal in the data volume”).
Here, at the remote base, a master that is communicable with all other secondary storage apparatus is configured among a plurality of secondary storage apparatuses. The secondary storage apparatus configured as the master acquires the time stamp contained in the latest journal among the journals retained in the respective journal groups configured in the self storage apparatus and the respective journal groups configured in the other secondary storage apparatuses (hereinafter referred to as the “intra-group latest time stamp”).
The secondary storage apparatus configured as the master mutually compares the acquired intra-group latest time stamp value of all journal groups, and controls the other secondary storage apparatuses so that the journals up to the time shown with the oldest intra-group latest time stamp are concurrently reflected in the respective secondary data volumes in accordance with such oldest intra-group latest time stamp.
According to this kind of remote copy technology, it is possible to replicate data in a remote base while maintaining the sequencing and consistency of the I/O data from the host across a plurality of journal groups.
Nevertheless, with the remote copy technology disclosed in Patent Document 1 and Patent Document 2, no consideration is given to cases where the data I/O load of the primary storage apparatus is different, and data transfer of the data volume and interval is periodically performed at the same level for the copying between all journal groups. Thus, there is a problem in that journals cannot be completely transferred to the remote base for journal groups having a high data I/O load.
Consequently, according to the foregoing remote copy technology, since the time difference of the latest time stamp will increase between journal groups, there is a problem in that the up-to-dateness of the data copied to a data volume in a journal group with a low data I/O load will be lost.
Although Japanese Patent Laid-Open Publication No. 2006-107450 (Patent Document 3) also discloses remote copy technology for performing data transfer and replication among a plurality of storage apparatuses while maintaining the sequencing, Patent Document 3 does not give any consideration to cases where the data I/O load is different between the primary storage apparatuses as described above.